Response of regeneration diversity of <Emphasis Type="Italic">Carex Lasiocarpa</Emphasis> community to different water levels in Sanjiang Plain,China     

Li Wang  Changchun Song  Jinming Hu  Tao Yang 《中国地理科学(英文版)》2010,20(1):37-42

The species diversity at the regeneration stage, inflenced by different water levels, is important for community composition in the later growing season. Regeneration diversity of Carex lasiocarpa community under different water levels was studied at two stages, recruitment and adult, in the Sanjiang Plain, Heilongjiang Province, China. The results showed that, at the two growing stages, important value of C. lasiocarpa population and species richness of the community decreased with the increasing water level, while the Simpson and Shannon-Wiener diversity indexes and Pielou evenness index increased. Under different water levels, community diversities were higher at the recruitment stage, while population important values of C. lasiocarpa were higher at the adult stage. Indexes in vegetation evaluation must be chosen prudentially for successful restoration and effective management of wetlands, and especially for wetland restoration, the optimal time should be selected according to the restoration objectives and costs.  相似文献   

Microhabitat effect on iron distribution and transfer in <Emphasis Type="Italic">Carex pseudocuraica</Emphasis> in Sanjiang Plain Wetlands     

Yuanchun Zou  Xianguo Lu  Ming Jiang  Xiaofei Yu 《中国地理科学(英文版)》2010,20(4):363-371

Ten clonal units of Carex pseudocuraica growing in four different microhabitats (perennial flooded ditch water, perennial flooded ditch sediment, seasonal flooded ditch sediment and perennial flooded soil) of the Sanjiang Plain, Northeast China, were collected randomly for phenotypic plasticity analysis. Iron content, chemical and physical properties of substrates and the total Fe of nine plant modules were measured as well. The results show that the performance of the C. pseudocuraica is affected by the microhabitat, with the greatest performance score in perennial flooded ditch water, and the lowest in perennial flooded soil. The biomass allocation indexes indicate that much more mass is allocated to stems and roots to expand colonization area. The distribution of the total Fe in plant modules appears as pyramids from the tip to the root, while marked differences are observed in the distribution proportion of stems, tillering nodes and roots that are allometrically growing. Iron transfer from substrates to the plant is mainly controlled by the substrate type. The differences of iron distribution and transfer in the plant in different microhabitats are attributed to the iron contents of the substrates as well as the phenotypic plasticity of the plant.  相似文献   

2008年深圳洪涝灾害的气候背景和环流条件   总被引：1，自引：1，他引：1  

王红军  刘文菁  刘培宁  潘维玉 《气象科学》2010,30(2):256-261

用NCC/CMA资料分析了2008年6月深圳降水异常事件的成因,结果认为:2007年7月—2008年2月赤道西太平洋海表温度异常偏低、2008年前冬今春青藏高原积雪面积偏大是深圳异常降水事件的前期气候背景;2008年6月东亚阻塞高压的异常强大及乌拉尔山长波槽的异常加深发展,促进了经向环流异常增强;偏强的冷空气以阶梯槽的形式频繁入侵华南,为深圳异常降水事件提供了动力条件。副高西段较常年偏南,西伸脊点偏东;强劲的季风潮为深圳地区输送了巨大的水汽和热量;冷暖空气在华南地区的频繁交汇与维持是深圳异常降水事件的主要成因。上述多种因素的异常共同导致了深圳异常降水事件的发生。  相似文献   

Air Quality,Climate, and Policy: A Case Study of Ozone Pollution in Tucson,Arizona     

《The Professional geographer》2013,65(4):469-491

This article addresses the need to better understand the complex interactions between climate, human activities, vegetation responses, and surface ozone so that more informed air-quality policy recommendations can be made. The impacts of intraseasonal climate variations on ozone levels in Tucson, Arizona from April through September of 1995 to 1998 are determined by relating variations in ozone levels to variations in atmospheric conditions and emissions of ozone's precursor chemicals, volatile organic compounds (VOCs) and nitrogen oxides (NO_x), and by determining month-specific atmospheric conditions that are conducive to elevated ozone levels. Results show that the transport of ozone and its precursor chemicals within the Tucson area causes the highest ozone levels to be measured at a downwind monitor. The highest ozone levels occur in August, due in part to the presence of the North American monsoon. Atmospheric conditions conducive to elevated ozone concentrations differ substantially between the arid foresummer (May and June) and the core monsoon months ( July and August). Transport of pollution from Phoenix may have a substantial impact on elevated ozone concentrations during April, May, and June, while El Paso/Ciudad Juarez –derived pollution may contribute significantly to elevated ozone concentrations in August and September. Two broad policy implications derive from this work. Regional pollutant transport, both within the U.S. and between the U.S. and Mexico, is a potential issue that needs to be examined more intensively in future studies. In addition, spatiotemporal variations in sensitivities of ozone production require the adoption of both NO_x and VOC control measures to reduce ozone levels in the Tucson area.  相似文献   

Late Triassic ammonoid Sirenites from the Sabudani Formation in Tokushima,Southwest Japan,and its biostratigraphic and paleobiogeographic implications     

Yasuyuki Tsujino  Yasunari Shigeta  Haruyoshi Maeda  Toshifumi Komatsu  Nao Kusuhashi 《Island Arc》2013,22(4):549-561

Discovery of Sirenites senticosus (Dittmar) in the upper part of the Sabudani Formation of the Kurosegawa Belt, Kito area, Tokushima Prefecture, Japan, establishes a late Early Carnian age for this part of the stratigraphic unit. Because S. senticosus was mainly distributed in the Tethyan region, its occurrence provides evidence that Late Triassic ammonoids of Japan had strong affinities with those of the Tethyan faunas. This finding clearly differs from the biogeographic distribution of contemporary bivalves in the region, which are referred to as the Kochigatani bivalve faunas, and show strong affinities to faunas of the Boreal region.  相似文献   

利用GRACE时变重力场探测2010年中国西南干旱陆地水储量变化   总被引：19，自引：4，他引：15       下载免费PDF全文

李琼  罗志才  钟波  汪海洪 《地球物理学报》2013,56(6):1843-1849

GRACE(Gravity Recovery And Climate Experiment)卫星计划为监测陆地水储量变化提供了有效技术手段.本文采用2003至2010年共计8年的GRACE月重力场模型反演中国西南区域陆地水储量变化,与GLDAS(Global Land Data Assimilation System)全球水文模型进行对比分析,其结果在时空分布上均符合较好,同时在2009年秋至2010年春该区域陆地水储量均呈现明显减少,与该时段云贵川三省的干旱事件相一致;比较分析了2009年秋至2010年春GRACE反演陆地水储量变化与TRMM(Tropical Rainfall Measuring Mission)合成数据计算的月降雨量的时空分布,两组结果均与西南干旱事件对应时段与区域十分吻合;对近8年的陆地水储量变化与月降雨量数据进行相关性分析,其结果表明陆地水储量变化与降雨量强相关,即降雨量是导致陆地水储量变化的主要因素;分析该区域地表温度变化,结果显示2009年9月至2010年3月地表温度均比历史同期高,地表温度的升高加剧了陆地水储量的减少.  相似文献   

The increasing predominance of extreme precipitation in Southwest China since the late 1970s          下载免费PDF全文

Guowei Zheng  Yang Li  Quanliang Chen  Xin Zhou  Guolu Gao  Minggang Li  Ting Duan 《大气和海洋科学快报》2022,15(5):100227

Extreme precipitation events cause severe environmental and societal damage worldwide. Southwest China (SWC) is sensitive to such effects because of its overpopulation, underdevelopment, and fragile ecosystems. Using daily observations from 108 rain-gauge stations, the authors investigated the frequency of extreme precipitation events and their contribution to total precipitation in SWC since the late 1970s. Results indicate that total precipitation is decreasing insignificantly, but rainfall-events frequency is decreasing significantly, whereas the region is experiencing more frequent and intense extreme precipitation events. Note that although fewer stations are statistically significant, about 60% of the rain-gauge stations show an increasing trend in the frequency and intensity of extreme precipitation. Furthermore, there is an increasing trend in the contribution of total extreme precipitation to total precipitation, with extreme precipitation becoming dominant in the increasingly arid SWC region. The results carry important implications for policymakers, who should place greater emphasis on extreme precipitation and associated floods and landslides when drafting water-resource management policies.摘要本文分析了中国西南20世纪70年代末以来极端降水事件的频率, 强度及其对总降水的贡献. 结果表明, 该地区约60%的降水站点极端降水的频率和强度正在增加, 而大多数站点总降水频率明显减少. 同时极端降水总量对总降水量的贡献有显著增加的趋势, 极端降水在日益干旱的中国西南地区变得更具主导性. 研究结果提醒应更加重视极端降水及其可能引发的次生灾害, 如洪水, 山体滑坡等.  相似文献   

三江北段纳日贡玛黑云母花岗斑岩LA-ICP-MS锆石U-Pb定年及其地质意义     

宋忠宝  贾群子  张雨莲  陈博  陈向阳  王富春  田永革  栗亚芝  张晓飞  全守村 《中国区域地质》2012,(2):439-447

西南三江北段是青海省重要的斑岩型铜钼矿成矿带,纳日贡玛铜钼矿是近年来在三江北段发现的与侵入岩有关的斑岩型铜钼矿。利用锆石U-Pb方法测得纳日贡玛黑云花岗斑岩的形成年龄为41.53Ma±0.24Ma,属于喜马拉雅早期。纳日贡玛斑岩型铜钼矿的成矿时代主要在40.86~40.80Ma之间。在多期热液叠加、多期成矿作用中,纳日贡玛斑岩型铜钼矿的热液应是纳日贡玛黑云花岗斑岩（41.53Ma±0.24Ma）和纳日贡玛斜长花岗斑岩（41.00Ma±0.18Ma）共同提供的。由于该区有较多的中酸性岩体存在,因而确定这些侵入体的形成年龄,对于在该区寻找同时代的斑岩型铜钼矿有重要的理论意义和现实意义。  相似文献   

黑龙江东部林口地区下白垩统穆棱组砾岩的成因及其意义     

张云鹏  任建业  赵学钦  汤艳  王珊  杨承志 《中国区域地质》2012,(10):1731-1738

大三江地区是中国东部重要的油气资源接替区,早白垩世时期该地区曾为一个统一的盆地,之后盆地遭受破坏分解。如何确定当时的盆地边界进而恢复盆地原型,是该地区亟待解决的关键地质问题之一。前人对盆地边界的确定大都以理论推测为主,缺乏实际证据。本次工作在黑龙江林口地区发现一套穆棱组底部砾岩,对砾石进行成分及分选特征、沉积特征等的统计与分析,结合古水流恢复和地震解释资料,认为该套砾岩整体为冲积扇相,以河道砾岩沉积和漫流砾岩沉积为主,物源主要来自盆地西部的张广才岭。结合地震资料分析,认为研究区穆棱组时期的沉积模型为冲积扇相向滨浅湖亚相的直接过渡。本研究不仅为大三江盆地西部边界的确定提供了直接证据,同时也为该地区今后的油气勘探指明了方向。  相似文献   

Geological and C–O–S–Pb–Sr isotopic constraints on the origin of the Qingshan carbonate-hosted Pb–Zn deposit,Southwest China     

《International Geology Review》2012,54(7):904-916

Located in the western Yangtze Block, the Qingshan Pb–Zn deposit, part of the Sichuan–Yunnan–Guizhou Pb–Zn metallogenic province, contains 0.3 million tonnes of 9.86 wt.% Pb and 22.27 wt.% Zn. Ore bodies are hosted in Carboniferous and Permian carbonate rocks, structurally controlled by the Weining–Shuicheng anticline and its intraformational faults. Ores composed of sphalerite, galena, pyrite, dolomite, and calcite occur as massive, brecciated, veinlets, and disseminations in dolomitic limestones.

The C–O isotope compositions of hydrothermal calcite and S–Pb–Sr isotope compositions of Qingshan sulphide minerals were analysed in order to trace the sources of reduced sulphur and metals for the Pb–Zn deposit. δ¹³C_PDB and δ¹⁸O_SMOW values of calcite range from –5.0‰ to –3.4‰ and +18.9‰ to +19.6‰, respectively, and fall in the field between mantle and marine carbonate rocks. They display a negative correlation, suggesting that CO₂ in the hydrothermal fluid had a mixed origin of mantle, marine carbonate rocks, and sedimentary organic matter. δ³⁴S values of sulphide minerals range from +10.7‰ to +19.6‰, similar to Devonian-to-Permian seawater sulphate (+20‰ to +35‰) and evaporite rocks (+23‰ to +28‰) in Carboniferous-to-Permian strata, suggesting that the reduced sulphur in hydrothermal fluids was derived from host-strata evaporites. Ores and sulphide minerals have homogeneous and low radiogenic Pb isotope compositions (²⁰⁶Pb/²⁰⁴Pb = 18.561 to 18.768, ²⁰⁷Pb/²⁰⁴Pb = 15.701 to 15.920, and ²⁰⁸Pb/²⁰⁴Pb = 38.831 to 39.641) that plot in the upper crust Pb evolution curve, and are similar to those of Devonian-to-Permian carbonate rocks. Pb isotope compositions suggest derivation of Pb metal from the host rocks. ⁸⁷Sr/⁸⁶Sr ratios of sphalerite range from 0.7107 to 0.7136 and (⁸⁷Sr/⁸⁶Sr)_200Ma ratios range from 0.7099 to 0.7126, higher than Sinian-to-Permian sedimentary rocks and Permian Emeishan flood basalts, but lower than Proterozoic basement rocks. This indicates that the ore strontium has a mixture source of the older basement rocks and the younger cover sequence. C–O–S–Pb–Sr isotope compositions of the Qingshan Pb–Zn deposit indicate a mixed origin of the ore-forming fluids and metals.  相似文献